Such seals are for example known from EP 1 236 002 B1.
Pipe seals of the above-mentioned type are used to seal pipes, in particular plastic pipes that are used in large pipe systems. Large pipe systems are usually built from a plurality of pipes that are affixed to each other. The pipes have one end at which their diameter is slightly enlarged to form a socket or bell so that they partially fit into each other, forming a kind of pipeline. The pipe seals seal off the space between the pipes and thus securely close in the medium that is transported by the pipe system. In particular, the pipes may be connected by means of bell-and-spigot joints or by loose couplers.
Pipe systems that are built this way are widely used for distributing and transmitting media such as potable water. In these systems, there are two factors that have to be observed in order to successfully hold the pipes together and keep the pipe system leak-proof.
Firstly, there is a constant pressure in the transported liquid which the pipe system needs to withstand. Secondly, there is thrust, which is a more dynamic component.
Hydrostatic and hydrodynamic forces that are unbalanced within a pipeline are referred to as thrust forces. Hydrodynamic thrust forces are mostly insignificant in public potable water systems due to the characteristic range of pressures and media velocities of municipal pressure pipe systems. In municipal applications such as water transmission and distribution as well as sewer force mains, thrusts occur whenever there is a change in the direction of flow, as is the case when fittings or other appendages are adjoined to a pipe. Thrusts also appear whenever there are changes in the cross-sectional area of the pipeline such as at reducers and during the opening and closing of valves and hydrants.
Thrust can cause separation of the pipe joints, in particular in bell-and-spigot push-on joints, if it is not counterbalanced with an equal and opposite reaction force. Common remedies for this problem include thrust blocks or lug-type mechanical joint restraint devices. These two approaches can also be combined and used together. Both thrust blocks and traditional joint restraints are arranged externally to a pipe system.
US 2009/0060635 A1 relates to a pipe seal having a sealing member and a carrier member. The carrier member is provided with a recess which is formed inside the carrier member for receiving a gripping ring. The gripping ring has about the same outer diameter as an inner surface of the recess formed inside the carrier member. Thus, the gripping ring is provided with a gap and is deformable to close the gap. This temporarily reduces the diameter of the gripping ring so that it can be set into the recess.
In EP 1 881 251 A2, retaining inserts are rigidly fixated in a support ring of a sealing element.